This invention relates to an apparatus for measuring a substance in vivo on the basis of bioluminescence, and more particularly to an apparatus for bioluminescence measurement suitable for measuring an intracellular substance in smooth muscles.
A conventional apparatus for measuring a substance in vivo on the basis of bioluminescence is disclosed in Science, Vol. 217 (1982), pp 252-254.
Intracellular C.sub.a.sup.2+ is a fundamental factor for controlling the entire cell activity and recently relations between changes in C.sub.a.sup.2+ concentration and various cellular functions have been extensively studied.
Several procedures have been proposed for the measurement of C.sub.a.sup.2+, and one of the procedures is based on bioluminescence, using aequorin, a photoprotein. This procedure based on the bioluminescence is regarded as the most sensitive among the now available procedures.
Measurement of intracellular C.sub.a.sup.2+ concentration was initially directed to suspended cells as being the most easily measurable ones, where a cell suspension containing about 10.sup.6 cells/ml was subjected to measurement of the concentration. As regards cells with tissues, the cells were freed from the tissues by decomposition and then brought into a suspended state, followed by the measurement of the concentration, because the aim of the initial research was to find whether changes in the concentration of intracellular C.sub.a.sup.2+ could be brought about by an external stimulus or not, rather than to find the relations between changes in the concentration and various cellular functions.
With increasing necessity for more accurate measurement of changes in the concentration, the measurement based on the decomposition of tissues has not been maintained, because the cellular activities are naturally influenced with adjacent cells.
Recently, a procedure for propagating cells on a glass plate and placing the glass plate in a cubic cell has been employed. Furthermore, another procedure has been proposed, where cells are propagated on the surface of a small sphere, and measurement is made of the small sphere by suspending it in a cell. However, these procedures present a difficulty in the preparation and handling of a sample.
Heretofore, a Petri dish has been usually used for cell culturing and is easiest to handle for the cell culturing. Thus, if such a dish can be set directly in the sample section in a luminescence-measuring apparatus after the incubation, a more precise measurement can be made with simpler cell culturing. However, temperature control is a problem in using the Petri dish. One of the reasons for selecting the measurement of cells cultured on the surface of a small sphere is this temperature control. Observation of cellular activities in vivo must be made under the same conditions as in vivo as much as possible, and thus the sample temperature must be kept constant at 37.degree. C. Thus, a sample container is usually set in a thermostat cell holder and a magnetic stirrer is placed in the cell to make the measurement with stirring. The stirring is indispensable for making the temperature constant in the sample cell. However, the stirrer cannot be used in the Petri dish, because it will peel the attached cells from the surface of the dish.